Comparision Of Seismic Performance Of Non-Isolated And Isolated Schemes Of A Highway Bridge

The planning highway line from Qingzhou to Linshu in national highway network from Changchun to Shenzhen, pass through the vicinity of several active seismic fault zones in the south of Shandong Province. The engineering sector paid much attention to the seismic design of new bridges in this region.Oriented to a new bridge under design, named Linyidong Zhuxian Bridge, two seismic schemes for the bridge are investigated. Scheme I is a non-isolated scheme with pot elastomeric bearings (PEBs), and restrainers are instralled between the pier and the superstructure. Schemeâ…¡is a isolated scheme with friction pendulum bearings (FPBs)in place of the pot elastomeric bearings in schemeâ… . The dynamic model of two schems are well developed, and dynamic propertied of the two schemes are compared. The seismic evaluation criteria are proposed, including the three-level objectives and design ground motions, and evaluation content and index are defined. Nolinear dynamic analysis approach is used for all the three earthquake levels. According to the specified evaluation criteria, the seismic performance of both schemes are evaluated and compared, and the ratio of capacity and demand for all the indice are calculated.The evaluation results of Schemeâ… indicate that for large earthquake level, lateral force capacity of the bearings in the fixed direction is insufficient. The lateral displacement capacity of the bearings in the movable direction is enough with the help of restrainers. The ductility and shear capacity of piers and piles are sufficient. For moderate earthquake level, only the pier with fixed bearings on top may yield. For small earthquake level, all the piers and piles are in elastic state.The evaluation results of Schemeâ… indicate that for major earthquake level, lateral force capacity of PEBs in the fixed direction is insufficient. The lateral displacement capacity of PEBs in the movable direction is enough with the help of restrainers. The ductility and shear capacity of piers and piles are sufficient. For moderate earthquake level, only the pier with fixed bearings on top may yield. For minor earthquake level, all the piers and piles are in elastic state.The evaluation results of Schemeâ…¡reveal that for major earthquake level, only a couple of piers may yield with less plasticity developed. The lateral displacement capacity of FPBs is sufficient without the addition of the restrainers, and FPBs has the self-centering capacity after the shock. FPBs can well eliminate the drawback of PEBs in poor shear capacity. Compared with non-isolated scheme, the isolated scheme is more efficient with higher safety redundancy.